I said 7 because I was averaging all of em. But really, I'd go by species and assign each a number from 5-10. The ones that love the reef crest environment like gemmifera? Probably a 9 or 10. Carduus or lokani for example? 5ish.
None are appropriate for first time reefers with no knowledge of chemistry or stability. You can start a tank with acros but be prepared for hard mode(TM)
None are appropriate for first time reefers with no knowledge of chemistry or stability. You can start a tank with acros but be prepared for hard mode(TM)